Question

1-3) Landfill leachate can be very strong, containing many different types of contaminants. To deal with these issues, biological treatment of the waste is often done using a series of well mixed steady state reactors. The Detroit Municipal Landfill uses two 25,000 L lagoons in series to treat the Nitrogen in their leachate. Under normal conditions, the leachate flowrate is 12,000 L/day and the first order Nitrogen degradation rate is 0.15 hour-1.

If the effluent Nitrogen concentration from the second reactor must be 0.5 mg/L to meet permit limits, what is the highest Nitrogen influent allowed into the first lagoon? 

A self-confident young engineer suggests the two 25,000 L lagoons should be merged to form one large 50,000 L lagoon. Assuming everything else remains the same, use calculations to show this engineer that they are incorrect.

Answer 1